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acute as the pulsations are frequent ; and the tone will also 

 be of a fine or agreeable quality in proportion as the pulsa- 

 tions are uniform and free from irregular vibrations. Thus, 

 if a common table be struck the sound is merely noise, 

 for although vibration is produced, yet the pulsations are 

 irregular and do not continue, for the material and form of 

 the table do not permit uniform or equal vibrations ; and if 

 the parts of a body vibrate in different and discordant periods, 

 the vibrations check each other, and soon cease. But if a 

 bell or a plate of metal freely suspended be struck, the 

 vibrations produced become regular in their periods, are 

 maintained a considerable time, and a musical tone is the 

 result. The velocity of the vibrations of the metal is found 

 to be in accordance with a function of the weight and the 

 elasticity of the metal put in motion; and the pitch, or 

 acuteness of the sound, is always in accordance with the 

 number of vibrations in a second of time, however the 

 vibration be produced. If a string be stretched over two 

 supports, technically called bridges, the string will naturally 

 remain at rest in the imaginary line between the supports, 

 and if removed from the line, will, when set free, return to 

 it, but the acquired velocity causes the string to pass the 

 line, and to make several oscillations on each side of it ; — 

 these oscillations or vibrations communicate themselves to 

 the surrounding air, and, as in the former examples, musical 

 tones result; and the number of vibrations per second is 

 found to be in accordance with the tension and the mass of 

 the string. Thus, if a string be stretched by a given weight 

 and the tone observed, and the weight be then doubled, the 

 tone will be found to be eight notes or an octave higher 

 in pitch than before, the velocity of the vibrations being 

 doubled; and if a string of half the weight to the same 

 length be substituted, and the like weight be used, the tone 

 will be found to be as high as when the thicker string and 



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